This invention relates to fluid pressures which incorporate non-metallic liners, and in particular to a seal system for forming a seal between a vessel access adapter device and the vessel liner.
Composite (fiber reinforced resin matrix) containers or vessels have come into common use for storage of a variety of fluids under pressure, including storage of oxygen, natural gas, nitrogen, rocket fuel, propane, etc. Such composite construction provides numerous advantages such as lightness in weight and resistance to corrosion, fatigue and catastrophic failure. This combination of lightness in weight and resistance to failure is possible due to the high specific strengths of the reinforcing fibers or filaments (carbon, glass, aramid, etc.) which, in the construction of pressure vessels, are typically oriented in the direction of the principal forces.
Because the resin matrix of the composite pressure vessel (shell) is subject to cracking and crazing during service and use, the vessels are oftentimes furnished with fluid impermeable liners. While metal liners are most common, elastomeric rubber and thermoplastic liners have become increasingly the liner of choice since thin metal liners (the thinness being necessary to reduce the weight) have low fatigue life. Advantageously, the liners are designed not only to prevent leaks from the vessel, but also to serve as mandrels during vessel fabrication, i.e., profile definition for the composite shell.
One problem with the use of non-metallic liners is that of securely attaching the liners to the vessel bosses which are typically metallic. The end-bosses support fluid passage into and out of the vessel and also may function in the fabrication of the composite shell by providing for fiber turnaround at the ends or poles of the vessel and for mandrel support if filament winding is used to construct the shell.
Although a number of prior art approaches have been suggested for attaching non-metallic liners to bosses, one approach which has proven desirable is disclosed in U.S. Pat. No. 5,494,188. In the arrangement described in the patent, a boss is employed which has a cylindrical neck portion, an annular collar extending radially outwardly from the neck portion, a central hollow or bore extending axially through the neck portion, and an annular groove formed in the bore to include downwardly and inwardly sloping shoulders on one side of the groove. The boss is disposed in an opening in the exterior composite structure shell. The liner also includes an opening aligned with the opening in the shell and the perimeter of the liner opening is formed with a radially inwardly projecting section for underlying the bottom of a collar of the boss and extending upwardly into the bore, over the shoulder and to the groove. An attachment mechanism is then disposed in the bore of the boss above the shoulder, to contact the liner section disposed over the shoulder.
It is desired that the seal between the attachment mechanism and the liner section positioned over the shoulder formed in the bore be as reliable as possible over wide temperature ranges including low temperatures.